Technical Abstract:
Bruises degrade the quality of apples and lower their value in the market. Therefore, development of effective techniques to detect and reduce bruises on apples is of utmost importance to ensure the quality of fruit. An experiment was designed and conducted to ascertain the potential of hyperspectral imaging for detecting bruises on Red Delicious apples. Red Delicious apples, free of visually detectable bruises, were obtained from local fruit packer and intentionally bruised by dropping them onto a flat, hard surface from two different heights (12.5 cm and 25.0 cm). Hyperspectral image data between 430 nm and 900 nm with a resolution of 3.74 nm were acquired from each test apple immediately before and after bruising and then at 1, 8, 15, and 29 days. The image data size was reduced and bruise features enhanced by using the principal component transformation technique. Results showed that bruised tissue had lower relative reflectance than normal tissue in the near-infrared region betwee 700 nm and 900 nm. A hyperspectral image processing procedure was successfully developed, which allowed us to identify all those intentionally created bruises on test apples as well as many pre-existing bruises. This research shows that hyperspectral imaging is capable of detecting apple bruises and has the potential for fruit grading applications.